Nowadays, more and more concern is focused on energy recycle for the sake of energy saving and environment protecting. Before a set of products are put on the market, they should experience lots of tests e.g. burn-in test so as to verify that the power parameters are within the specified tolerances with a minimal consumption of electric power by the power supply.
Generally speaking, a power supply has to undergo burn-in test for several hours to verify its reliability and stability. Conventional burn-in test system for power supply uses a resistor tank as the load. In this case, a large amount of energy is transformed into heat and dissipated thereby, which causes additional energy consumption dissipated by the air-conditioning system. In order to save energy consumption and reduce the cost of burn-in test, an energy recycle mechanism is usually provided in the burn-in test system in order to avoid the dissipation of the redundant energy. In recent years, the energy recycle technique used in burn-in test for DC power supply and uninterruptible power supply (UPS) has been extensively employed. FIG. 1 shows the circuitry of an energy recycle system used in a burn-in test system for DC power supply. As shown in FIG. 1, the energy recycle system 100 includes a boost converter 102 for drawing a load current from a DC power supply (not shown) and converting one or more output DC voltages of the DC power supply into an appropriate DC voltage, and a buck converter 104 for descending an output voltage of the boost converter 102 to a desired DC voltage. The energy recycle system 100 further includes a DC-AC converter 106 for converting an output DC voltage of the buck converter 104 into an AC voltage, and an output filter 108 for removing the high-frequency harmonics from the output AC current of the DC-AC converter 106. The output AC current of the output filter 108 is injected into the utility grid, thereby accomplishing the energy recycle operation. Because the boost converter 102, the buck converter 104 and the DC-AC converter 106 have high energy conversion efficiency, most of the energy can be delivered to the utility grid. As to the electronic ballast used for igniting gas discharge lamps such as fluorescent lamps, it also needs to undergo burn-in test. It is well known by those skilled in the art of power supply, the output of an electronic ballast is an AC current source having a frequency of 30 to 60 kHz. Therefore, an electronic ballast can be considered as an AC current power supply. In normal conditions, discharge lamps would show resistive characteristics. Therefore, electronic ballasts usually select power resistors as the load for burn-in test. Under this condition, a large amount of energy is converted into heat and dissipated thereby, which would cause additional energy waste in the air-conditioning system.
Therefore, an energy recycle system using with an AC current power supply for energy saving is proposed, so that the energy can be delivered to the utility grid with minimal power loss.